1. Field of the Invention
This invention relates to a novel class of heterocyclic compounds useful for selectively inhibiting trypsin-like enzymes, selectively inhibiting chymotrypsin-like enzymes, selectively inhibiting elastase or for generally inhibiting serine proteases of all classes. This invention also relates to a method of controlling blood coagulation, complement activation, fibrinolysis, and tumor invasiveness and treating inflammation, blistering, and viral infection in patients using the novel compounds of the present invention. We have found that isocoumarins substituted with basic groups are potent inhibitors of blood coagulation enzymes, tryptases and plasmin, and isocoumarins substituted with hydrophobic groups are potent inhibitors of chymases and elastases, therefore they are useful as anticoagulants, anti-inflammatory and anti-tumor agents.
2. Description of the Related Art
Serine proteases play critical roles in several physiological processes such as digestion, blood coagulation, complement activation, fibrinolysis, viral infection, fertilization, and reproduction. Serine proteases are not only a physiological necessity, but also a potential hazard if they are not controlled. Blood coagulation serine proteases are responsible for vascular clotting, cerebral infarction, and coronary infarction. Plasmin and plasminogen activator are involved in tumor invasiveness, tissue remodeling, blistering, and clot dissociation. Uncontrolled proteolysis by elastases may cause pancreatitis, emphysema, rheumatoid arthritis, bronchial inflammation and adult respiratory distress syndrome. It has been suggested that a new trypsin-like cellular enzyme is involved in the infection of human immunodeficiency virus type 1 [HIV-1; Hattori et al., FEBS Letters 248, pp. 48-52 (1989)], which is a causative agent of acquired immunodeficiency syndrome (AIDS). Accordingly, specific and selective inhibitors of these proteases should be potent anticoagulants, anti-inflammtory agents, anti-tumor agents and anti-viral agents useful in the treatment of protease-related diseases [Powers and Harper, Proteinase Inhibitors, pp. 55.152 (Barrett and Salvesen, eds., Elsevier, 1986), incorporated herein by reference]. In vitro proteolysis by trypsin, chymotrypsin or the elastase family is a serious problem in the production, purification, isolation, transport or storage of peptides and proteins.
Anticoagulants and antithrombotic drugs are used in a variety of thrombotic disorders. The 1986 Physician's Desk Reference list three anticoagulant drugs (heparin, protamine sulfate and warfarin), one antiplatelet drug (aspirin) and several thrombolytic agents. Heparin and warfarin are commonly used clinically for prevention and treatment of venous thrombosis and pulmonary embolism. Heparin inhibits the blood coagulation activity by accelerating the binding of natural plasma protease inhibitor antithrombin III with coagulation factors, and warfarin acts as a vitamin K antagonist and inhibits the synthesis of coagulation factors. None of the anticoagulant drugs, antithrombotic drugs, fibrinolytic agents and antiplatelet drugs are highly effective in all clinical situations and many induce side reactions [Von Kaulla, Burger's Medicinal Chemistry, Part II, pp. 1081-1132 (Wolff ed., 1979), incorporated herein by reference]. Coagulation disorders such as disseminated intravascular coagulation, bleeding complications of medical and surgical procedures and bleeding complications of systemic illness are still difficult to manage [Ingram, Brozovic and Slater, Bleeding Disorders, pp. 1-413 (Blackwell Scientific Publications, 1982), incorporated herein by reference]. In the treatment of patients with coagulation problems, anticoagulant or antithrombotic agents of diverse mechanisms are urgently sought in order to provide better medical care.
Anti-inflammatory agents are used to treat elastase-associated inflammation including rheumatoid arthritis and emphysema. Although the naturally occurring protease inhibitor, .alpha.1-protease inhibitor (.alpha.1-PI) has been used to treat patients with emphysema, this inhibitor is not widely used clinically due to the high dosage needed for the treatment and difficulty of producing large quantities. Therefore small molecular weight elastase inhibitors are needed for therapy.